Human moral behaviour ranges from vicious cruelty to deep compassion, and any explanation of morality must address how our species is capable of such a range. Darwin argued that any social animal, with sufficient intellectual capacity, would develop morality. In agreement, I argue that human morality is unique in the animal kingdom not because of any particular moral capacity, but because some very abstract cognitive abilities that are unique to our species are layered on top of phylogenetically older emotional instincts (...) for aggression and for empathy. I review research on several components of empathy, intersubjectivity and theory of mind, detailing which of these capacities is uniquely human, and highlighting relevant neuroanatomy for each ability. Finally, I describe our abstract cognitive abilities for recursion and metarepresentation, and argue that these are uniquely human. When these abilities interact with our older social abilities (empathy, intersubjectivity) we are able to reason abstractly about others' mental states and how to affect them. Thus, it is these abstract cognitive capacities that give us the ability to be both cruel and compassionate, but it is our ancient ability for empathy that keeps us moral. Morality is, in a very real sense, a gift from our ancestors. (shrink)